1. Field of the Invention
The invention relates to an anchoring screw that has triple threads of different depths of thread and particularly to an anchoring screw for fastening to cement walls (or other construction panels and boards).
2. Description of the Prior Art
Referring to FIG. 1, a conventional method for mounting or hanging articles on a cement wall 1 (or other construction boards and panels) usually is done by fastening an expanded screw 2 into a construction hole 11, then installing a bolt 21 therein for mounting or hanging an article or object desired. Such a construction method has many problems, notably:                1. Anchoring of the expanded screw 2 requires to use a special pliers or tool to pull the conical front end 211 of the bolt 21 to expand the nail fastener 22 to firmly engage with the construction hole 11. The cement wall is prone to crack during the expansion process. It is a big disadvantage of using such type of expanded screw.        2. Installing the expanded screw 2 requires a special pliers or tool, and makes construction work inconvenient.        3. Once the expanded screw 2 is installed and anchored in the construction hole 11, it is very difficult to remove.        4. As the expanded screw 2 tends to cause the cement wall crack around the construction hole, the interval between the construction holes must be increased to a longer distance, especially on the corners of the walls. As a result, the number of construction holes for a unit area of the wall surface is limited, and the coupling strength between the wall and boards is affected, and the number of articles or objects that can be supported or hung is restricted.        